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One poll compilation gives the “Remain” side a two percentage point edge; another gives it a one percentage point edge; a third has “Brexit” very slightly ahead.

But based on how voters behaved in other high-stakes referendums — Quebec’s on seceding from Canada in 1995 and Scotland’s on leaving the United Kingdom in 2014 — we can expect Britain to stay in the EU by at least a few percentage points, McGill University political scientist Eric Bélanger argues.

In the final weeks before the 1995 Quebec vote, the “Yes” side started to take a convincing lead, though about 10 per cent of voters were still undecided. Two days before the historic vote, the “Yes” side’s lead was up to six percentage points. But in the end, Quebec decided to stay in Canada by a tiny margin of just over one percentage point.

Nineteen years later, Scottish voters faced a similarly high-stakes decision about whether to leave the U.K. In that case, the “No” option saw a narrow but widening lead — five percentage points in the last days of the campaign. But in the real vote, Scots rejected independence by twice that margin, over ten percentage points.

In both cases, the side that was against the proposed change gained a five-point margin in the real vote that wasn’t visible in the polls. In both Scotland and Quebec, the separatist vote stayed loyal and steady to the end, but undecided voters came out disproportionately to oppose them.

WATCH: Polls opened in Britain on Thursday morning for a referendum on whether the country should quit the European Union bloc it joined 43 years ago. Jeff Semple reports.

“This has been called the ‘status quo bias,’” Bélanger explains. “Voters start to see that maybe it’s going to happen, maybe the change option will win, and they start to question themselves and rethink their voting intentions.”

“Those who don’t really have an opinion will, when they have to cast their ballot, they tend to favour the status quo option.”

High-stakes referendums have far higher voter turnout than normal elections — Scotland’s had 84 per cent and Quebec’s had over 93 per cent.

So there’s a strong sense of civic obligation at work, but among those swept up in the moment are many with no strong view, and they seem to vote for the devil they know, whatever that particular devil might be.

WATCH: Professor Anand Menon from King’s College in London discusses tomorrow’s referendum, which will decide whether Britain will stay in or leave the European Union.

So if the Brexit referendum follows the patterns from Scotland and Quebec, we can expect about a 52-48 result in favour of Britain staying in the EU.

“I think ‘Remain’ will win by a slight margin,” Bélanger predicts.

That narrow a victory would be the most lukewarm possible embrace of Britain’s place in the EU, however. It would be the Union’s third major humiliation in recent years, after the euro crisis and the perceived mishandling of the refugee crisis.

On Thursday, the markets appeared to be betting against Brexit, as the value of the pound rose.

On the other hand, torrential rain and flooding today in London and the southeast forced polling stations to close, and will have discouraged many from voting — especially less motivated voters who would tend to vote against Brexit.

Polls show that the region strongly favours staying in the EU. Low turnout there would be a serious blow to the Remain side.

Also, a poll published today showed that only 67 per cent of voters would definitely cast a ballot today, a low number for a high-stakes referendum. It also predicted low turnout among younger voters and high turnout among older voters, a factor that tends to favour Brexit.

“A poor turnout risks people viewing this issue as unclosed, and we could see calls for further referendums or questioning of the validity of the result from either side,” wrote Katie Ghose, head of the Electoral Reform Society, which commissioned the poll. “The fact that turnout could be similar or lower than last year’s general election is a shame if true.”